Solar power is becoming a more commercially acceptable and economically viable source of energy, due in part to the increasing costs of fossil fuels. With some solar energy systems, mirrors are used to reflect and concentrate or focus solar energy for purposes including, for example, heating a fluid and/or generating electricity. Mirrors that are capable of reflecting a sufficiently high level of solar radiation can be used in concentrated solar thermal power (CSTP) installations. Numerous mirror geometries can be used with CSTP installations. Typically, curved parabolic solar mirrors are used to concentrate solar energy onto conduits positioned along a focal line of the parabolic mirrors. A heat transfer fluid passing through the conduits carries absorbed heat energy to a generator station where it is used for power generation, such as electricity. Another known CSTP system is composed of a vertical solar tower surrounded by a number of pivotally adjustable flat solar mirrors, which reflect and direct solar energy at a particular location on the vertical tower. The heat generated by the solar energy focused on the vertical tower is transferred to a heat transfer material, and the heated and/or molten transfer material is used for power generation.
Other solar energy systems involve the use of solar mirrors to reflect and concentrate or focus solar energy onto high-efficiency photovoltaic (PV) devices, so as to increase or maximize the energy output for each PV device. Such solar energy systems are typically referred to as concentrated photovoltaic (CPV) systems.
Mirrors used in such solar energy systems are typically required to reflect a maximum level of solar energy. At the same time, such mirrors are also required to have a long service life, for example, having a minimum reduction in reflectance as a function of time, so as to minimize the need for replacing the mirrors.
Mirrors, and in particular solar mirrors which are typically exposed to outdoor environments, are prone to edge and surface corrosion, which can result in reduced reflectance of the mirrors. The reflective layer or layers of the mirror are often degraded due to the effects of corrosion. To reduce corrosion, mirrors are typically fabricated with one or more lead containing layers, which are typically sacrificial layers. Mirrors fabricated with lead containing layers generally have a reduced level of corrosion and longer life. The presence of the lead-containing layers can, however, represent an environmental hazard during fabrication and/or disposal of the mirrors. Addressing lead related environmental hazards can increase production and/or disposal costs associated with such mirrors.
It would be desirable to develop new mirrors, such as solar mirrors, that have a combination of high reflectance, high resistance to corrosion, and long life. It would be further desirable that such newly developed mirrors be free of lead containing layers.